We have conducted studies showing that the the LAR family of receptor protein tyrosine phosphatases are are binding partners for proteoglycan GAG chains. The binding of the different family members are not all the same. We have identified different regions in the extracellular domains of these molecules that bind GAG chains with different sulfation patterns. We have identified a novel binding site in Receptor Protein Tyrosine Phosphatase Sigma that binds Heparin Sulfate. In addition our data point to an additional receptor that binds bioactive CSPGs. A publication describing these results is in preparation. We demonstrated the the Lipid Phosphate Phosphatase-Related Proteins (LPPRs) act in concert to modulate cellular physiology. We find that they associate with each other in cells, and that this association increases the bioactivity of these proteins. A paper describing these results was published. We have created knockout mice for the LPPR-1 and LPPR-3 and are now characterizing these mice. We have initiated studies on the effect of xylosides, compounds that are used to alter proteoglycan GAG chain somposition, showing that, at concentrations lower than those previously reported to be effective, they have other actions on cellular physiology. In collaboration with Dr. Jeffrey Urbach of Georgetown University, we demonstrated that growing axons respond to changed in confinement by altering their rate of growth. They do not respond to confinement per se, but to changes. These results were published.